### event horizon

**(EH)**
(surface-shape around a black hole through which light cannot escape)

A black hole's **event horizon** is the surface-shape
around the black hole consisting of the points through which
electromagnetic radiation cannot escape from whatever is within.
It is considered that there is no way to find out what
is within the event horizon other than its mass, rotation,
and charge. It can be thought of as the physical size of the black
hole, which may be useful for some approximate models, but the
weirdness of black holes means there are caveats.

For the simplest black hole (no rotation or charge), the event
horizon is at the Schwarzschild radius (2GM/c²) from the
black hole's center. Any rotation makes it "wider" (as it would a
planet or star), but likely doesn't change the order-of-magnitude.

(*black holes*)
**Further reading:**

http://en.wikipedia.org/wiki/Event_horizon

**Referenced by pages:**

black-hole information paradox

black hole shadow

black hole thermodynamics

black hole (BH)

Event Horizon Telescope (EHT)

electron degeneracy

ergosphere

Hawking radiation

law of cosmic censorship

neutron degenerate matter

photon sphere

quantum fluctuations

Schwarzschild radius

gravitational singularity

SMBH formation

superradiance

Index